Explorers have discovered the world's deepest known underwater cave in the Czech Republic, with a depth of at least 1,325 feet, or 404 meters.

Krzysztof Starnawski / AP

Czech Republic is seen examining the limestone crevasse in the flooded Hranicka Abyss.

The flooded limestone fissure is so deep, four Statues of Liberty could be stacked on top of each other and still not reach the surface.

Krzysztof Starnawski / AP

And the Hranicka Propast, or Hranice Abyss, could still set more records since the underwater robot sent down to explore the deepest area was constrained by its cord — before reaching the bottom.

Polish explorer Krzysztof Starnawski told the Associated Press on Friday that he felt like a "Columbus of the 21th century."

Starnawski, 48, made the discovery on Tuesday after scuba diving down to a narrow passage in the cave about 200 meters down, where he then launched an underwater robot that made it 404 meters, or 1,325 feet, below before it was held back by its cord.

The Czech Speleological Society said "it was as deep as its rope could go, but the bottom was still nowhere in sight," the AP reported.